In the June 1 edition of Cell, researchers describe a way to electrically stimulate areas deep within the brains of mice using electrodes placed on the scalp. If further research bears out these early results, the technique might eventually provide an alternative to deep brain stimulation, which uses surgically-implanted electrodes, as therapy for Parkinson’s disease (PD).
Deep brain stimulation (DBS) has helped many people with PD who live with disabling tremors, wearing-off episodes and troubling dyskinesias. However, surgery to implant electrodes deep within the brain carries risks, and some people have experienced side effects related to speech and cognition. Scientists have been searching for ways to achieve the benefits of DBS without surgery.
Researchers led by Edward S. Boyden, Ph.D., at the Massachusetts Institute of Technology, devised a way to deliver electrical stimulation to specific areas deep within the brain, using electrodes placed on the scalp. The technique takes advantage of a phenomenon known as temporal interference. Electrodes, when delivered individually, deliver high-frequency currents that pass through the brain with no effect. But where the electrode beams cross, or interfere, a small region of low-frequency current is generated, which activates neurons. Researchers tested the technique in the physics lab and in experiments with laboratory mice.
- In mice, the researchers stimulated a deep brain region called the hippocampus, which is associated with memory.
- Researchers were able to guide the stimulation to neurons in different parts of the motor cortex, and prompt mice to move their legs, ears or whiskers.
- By tuning the frequency of the currents and changing the number and location of the electrodes, the researchers could control the size and location of the brain tissue receiving the low-frequency stimulation.
- The technique did not activate neurons in the brain’s cortex, the region lying between the electrodes on the skull and the hippocampus.
What Does It Mean?
The major limitation of deep brain surgery is the one to two percent chance of major complications, such as stroke or intracranial hemorrhage.
If researchers could find a way to reach the nuclei deep in the brain without inserting electrodes it could be groundbreaking. The Parkinson’s community would welcome a nonsurgical way to achieve the benefits of DBS.
The technique investigated has potential to be developed as a therapy for PD; however, the current study investigated the methodology in mice and not humans. Given the major differences in brain and skull size, studies on animal models which resemble humans more closely, i.e., primates, may be the next step.
Further research is needed to prove that the method is safe and effective, as well as practical. In particular, as a PD therapy, electrical stimulation would need to be focused more precisely, and on smaller brain areas. In addition, treating PD might require a way to provide continuous electrical stimulation from a portable, or wearable technology. Another noninvasive method for stimulating the brain — transcranial magnetic stimulation (TMS) — also is under investigation as a PD therapy, with mixed results so far.